1. Field of the Invention
The present invention relates to an elastically deformable antenna reflector for a spacecraft, such as an artificial satellite or space probe. It also relates to a spacecraft provided with at least one such reflector.
2. Description of Related Art
It is known that the items of equipment, such as the antennae, solar panels, etc, associated with a spacecraft have to be able to be folded in order to be able to be accommodated in a launch vehicle (rocket, shuttle) and to be deployed after ejection out of said launch vehicle, so as to take up their operational configuration.
It is known, moreover, that such equipment has already been produced in such a way that it is elastically deformable, this equipment then being able to take up either a deployed state, or a folded state, elastically deformed. For example, U.S. Pat. No. 3,521,290 describes an antenna reflector in a single piece of an elastically deformable material provided with a rigid central base to which are linked a plurality of radial ribs integral with the convex face of said reflector and elastically articulated to said central base. Thus, said antenna reflector can take up a position folded into the shape of a tulip, which does not risk entailing permanent deformation of said reflector, and the change from the folded position into the deployed position in the shape of a concave disk can be carried out under the action of the elastic energy stored during the folding of the antenna structure. Controllable retaining means, consisting of a belt with pyrotechnic bolts, surrounding said folded reflector and arranged on the side opposite said central base, are provided in order to hold said reflector and said radial ribs in folded position under stress.
U.S. Pat. No. 4,133,501, which describes a single-piece solar panel for a spacecraft produced in an elastically deformable way in order to be able to take up either a curved, folded position under stress for which said solar panel matches the convex outer surface of said spacecraft, or a flat, deployed position, clear of said outer surface, the change from the curved, folded position to the flat, deployed position being due to the elastic relaxation of said solar panel. In curved, folded position, the solar panel is held against the outer surface of said spacecraft by latches, carried by the spacecraft; and U.S. Pat. No. 4,926,181, which describes a single-piece antenna reflector of an elastically deformable material, which can be rolled into a cylindrical shape and held in this shape by clamps. An underlying pliable structure can be deployed, in order to serve as a support on which said reflector can unroll and take up its deployed, operating shape, under the action of its elastic relaxation.
U.S. Pat. No. 5,644 322, which describes an antenna reflector consisting of a central rigid base of large surface area, surrounded by a peripheral frustoconical ring, produced from an elastically deformable material. This prior document shows, moreover, that it is usual, for launching a spacecraft, to store it in an elongate casing, for example of cylindrical-conical shape, constituting, for example, the upper nose cone of the launch rocket, the reflector of the antenna or antennae of said spacecraft being arranged laterally with respect to the body of the latter in the peripheral space bounded between said body and said casing. By virtue of the structure of the reflector of the U.S. Pat. No. 5,644,322, the size of said reflector, within said cylindrical-conical casing, can be slightly reduced by temporarily elastically deforming said peripheral ring, said reflector then taking up the shape, at least approximately, of a bowl laterally enveloping said body. The reflector is kept in this bowl shape by a belt, loosening of which is controlled electrically and which surrounds said body and said reflector in the central region of said base, this belt folding said elastically deformable ring down onto said body, bearing on two diametrally opposite points of said ring. After ejection into space, said reflector can resume its operating position, by removal of said belt and elastic return of said peripheral ring to its elastically relaxed, stable, deployed position. It can easily be understood that, in such a device, the saving in size of said reflector in folded position, by comparison with the deployed position, is limited. This is, on the one hand, due to the large diameter of said rigid central base, the lateral compression of the reflector can be applied only to the peripheral ring, such that the saving in the lateral size is relatively small. On the other hand, this lateral compression not only exerts no reducing action on the longitudinal dimension of said reflector, but further increases said dimension due to the fact that it entails the straightening of the upper part of said peripheral ring outward. The longitudinal size of the reflector, in folded position, is thus greater than that of its deployed position. However, because of its dimensions, said reflector generally overshoots the upper longitudinal end of the body of said vehicle housed in the cylindrical part of the casing and has to be extended into the conical part thereof. This conical shape thus imposes a limitation on the diameter of the reflector. However, for obvious reasons of performance, it would be advantageous for the reflector to be able to have as large a diameter as necessary, and to match the convergent shape of the conical part of the casing.
U.S. Pat. No. 5,574,472 and EP-A-0 534 110 describe an antenna reflector in a single piece of an elastically deformable material, which can take up a bowl-shaped folded position by virtue of a controllably frangible tensile link arranged between two diametrally opposed points of the periphery of said reflector. It will be noted that, in this position folded into a bowl shape, the upper peripheral edge of the reflector, projecting outward with respect to the body of the spacecraft, is straightened outward and cannot therefore be housed in the conical part of the casing. Moreover, it will be noted that said tensile link constitutes an obstacle, or at least an impediment, in arranging the body of the spacecraft in the concave space of the reflector in folded position, and that the production of said reflector in a single piece allows neither precise control of the shape of the reflector in folded position, nor optimal enveloping of the body of the spacecraft.